G.f. satisfies A(x) = 1 + x*A(x)^4 / (1 + x*A(x)^4).

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =43a(5) =170a(6) =657a(7) =2392a(8) =7675a(9) =17603a(10) =-11898a(11) =-529678a(12) =-4783303a(13) =-33099464a(14) =-201744488a(15) =-1130700432a(16) =-5917753701a(17) =-28985131575a(18) =-131668554663a(19) =-540199800203